Hi all! The lawnmower's owner told me that they couldn't engage the blade but didn't know why. They had changed the blade and it stopped working. I looked under the machine and noticed the PTO arm had sheered off. They also said the deck wasn't level so that may have contributed to the stress on the part--not sure!
This repair takes longer than you think because you need to remove the entire shell. I found the trickiest part to be getting the throttle cable off.
UPDATE: I made a mistake in the video and the PTO correctly installed should look like in the thumbnail in the video (I had it backwards originally). If it would be helpful I can put the real image on a message board--just let me know!
PTO Arm: Honda 75194-771-010